function createXMLHttpRequest(){ 
    try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) {} 
    try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) {} 
    try { return new XMLHttpRequest(); } catch(e) {} 
    alert("XMLHttpRequest no soportado"); 
    return null; 
} 
 
onload=function(){

	if (document.getElementsByClassName == undefined) {
		document.getElementsByClassName = function(className)
		{
			var hasClassName = new RegExp("(?:^|\\s)" + className + "(?:$|\\s)");
			var allElements = document.getElementsByTagName("*");
			var results = [];

			var element;
			for (var i = 0; (element = allElements[i]) != null; i++) {
				var elementClass = element.className;
				if (elementClass && elementClass.indexOf(className) != -1 && hasClassName.test(elementClass))
					results.push(element);
			}

			return results;
		}
	}

    blocked = 0; 	
	var ad_nodes = document.getElementsByClassName(ads);
	for(i in ad_nodes){
		if (ad_nodes[i].offsetHeight == 0){ 
			blocked = 1;
			//ad_nodes[i].innerHTML = msg;
			alert(msg);
		}
	}
}